Global Positioning System (GPS) and other like satellite positioning systems have enabled navigation services for mobile handsets in outdoor environments. Since satellite signals may not be reliably received and/or acquired in an indoor environment, different techniques may be employed to enable navigation services. For example, mobile devices can typically obtain a position fix by measuring ranges to three or more terrestrial wireless access points which are positioned at known locations. Such ranges may be measured, for example, by obtaining a MAC ID address from signals received from such access points and measuring one or more characteristics of signals received from such access points such as, for example, signal strength, round trip delay, just to name a few examples.
In some implementations, an indoor navigation system may provide a digital electronic map to mobile stations as they enter a particular indoor area. Such a map may show indoor features such as doors, hallways, entry ways, walls, etc., points of interest such as bathrooms, pay phones, room names, stores, etc. Such a digital electronic map may be stored at a server to be accessible by a mobile device through selection of a URL, for example. By obtaining and displaying such a map, a mobile device may overlay a current location of the mobile device (and user) over the displayed map to provide the user with additional context.
In some implementations, in addition to a digital electronic map, an indoor navigation system may selectively provide positioning assistance data to mobile stations to facilitate and/or enable location based services (LBS). Such positioning assistance data may include, for example, information to facilitate measurements of ranges to wireless access points at known fixed locations. For example, “heatmap” or “radio map” data indicating expected RSSI and/or round-trip delay times associated with access points may enable a mobile station to associate signal measurements with locations in an indoor area. Here, grid points may be laid over locations in an indoor interval at uniform spacing (e.g., two-feet separation of neighboring grid points). Heatmap metadata may be made available from a local server for each grid point covering an indoor area. Other positioning assistance data may include locations of transmitters, routeability graphs, probability heatmaps, digital maps for display, just to name a few examples.